Black water tank fills with no usage

[Comm1]

UPDATE ---- We tested the sink and it DOES drain into the rear black tank.
Since reading the information on this forum --- THANK YOU ALL --- we contacted three local RV dealers that sell Coachmen and asked them where the rear sink drains into and all of them said the gray tank. We read through the "RV Owner's Kit," AKA "owner's manual," and it states sinks / shower to gray, toilets to black.
We were ready to call Coachmen and ask them when we noticed on the digital version of the "RV Owner's Kit" under plumbing, waste water / holding tanks, there is a video on the waste water system. The video states "As a general rule, sinks are plumbed to the gray water system, but in some cases they may be plumbed to the black water tank."
Wow!! Why could they not put that information in the owner's manual? What about people who don't rely on a computer for all of their information? Especially when the dealer's don't seem to be informed, either. Go figure!
Thanks again everyone!!

[jtsriding]

Originally Posted by Dirt Sifter

Glad the OP got the info he needed. I am often impressed by how old RVer's forget how little they knew about RVing when they first started or changed rigs. So fortunate to have those who strive to make positive contributions to help solve issues.

Well said... I was thinking the same thing.